1. Field of the Invention
The present invention relates to an electrostatic discharge protection device, and, more particularly, to an electrostatic discharge protection device having a metal shell.
2. Description of the Related Art
With the growth of technology, typical consumers prefer smaller portable electronic devices. However, these smaller electronic devices, with polymer materials, often suffer from electrical overstress (EOS) damage caused by electrostatic discharge (ESD). Therefore, an important issue concerns providing electrostatic discharge protection for these smaller electronic devices.
Please refer to FIG. 1A. FIG. 1A is a schematic drawing of a prior art electrostatic discharge protection device. A lid switch 94 is taken as an example; the lid switch 94 is electrically connected to an electronic device 90a via a signal wire 93a and a connection port 96a. The lid switch 94 is connected to a grounded end 921a via a ground wire 92a, which is used as an electrostatic discharge protection device. However, the lid switch 94 is made of a plastic material that is not a very good conductive material for static charge. Therefore, the lid switch 94 may collect a large amount of static charge and damage the electronic device 90a. 
Please refer to FIG. 1B. FIG. 1B is a schematic drawing of another prior art electrostatic discharge protection device. A microphone 95 is taken by way of example. The microphone 95 is electrically connected to the electronic device 90b via the signal wire 93b and the connection port 96b. The microphone 95 utilizes a metal shell 91 to cover the microphone 95, and the microphone 95 uses the ground wire 92b to connect to a grounded end 921b for use as an electrostatic discharge protection device. However, the metal shell 91 is not directly connected to the grounded end 921b, and so static charge cannot be discharged. When the static charge cannot be discharged, a voltage arc may occur to the signal wire 93b of the microphone 95, which will cause damage to the microphone 95 or even short-circuit the electronic device 90b. In the prior art technology, a suppression component is added to the circuit of the ground wire 92b and the signal wire 93b to suppress the static electricity. However, the suppression component 97 does not provide very good performance and also increases manufacturing costs.
Therefore, it is desirable to provide an electrostatic discharge protection device to obviate the aforementioned problems.